In general, in a state where a psychological burden is placed on a person, specifically, in a state where the person is stressed to be tense (referred to as a stressed state), a so-called strain or stiffness corresponding to an involuntary excessive muscle activity appears. The muscle activity appearing as the strain or stiffness in the stressed state is called a stress-related muscle activity. As a technique which treats the stress-related muscle activity, for example, Patent Document 1 described below is cited. In Patent Document 1 described below, when a certain type of operation is performed, muscles which have no direct relation with the operation are selected. For the selected muscles, muscle activity information is acquired. From the stain or stiffness appearing in the muscle activities of the muscles, the degree of stress (the degree of the psychological burden) on the person is evaluated. For example, for a clenching action performed by a person during an operation (worker) when the worker feels stressed, the muscle activity information indicating the degree of the muscle activity related with the clenching is acquired. Based on the acquired muscle activity information, a state of tension of the worker is evaluated. The use of the stress-related muscle activity allows, for example, the evaluation of the state of tension with a higher time resolution as compared with the case where general stress indices (for example, those obtained by the analysis of a heartbeat interval, sweating, urine components, salivary components, blood components, and the like) are used.
Patent Document 1: JP 2005-87486 A